Glossary
Glossary–61502C MTDR User Manual
denote changes resulting from environmental influences, such as tempera-
ture, humidity, vibration, and shock.
TDR
An acronym for Time-Domain Reflectometer. These instruments are also
called cable radar. They send out pulses of energy and time the interval to
reflections. If the velocity of the energy through the cable is known,
distances to faults in the cable can be displayed or computed. Conversely, the
speed that the energy travels through a cable of known length can also be
computed. The way in which the energy is reflected and the amount of the
energy reflected indicate the condition of the cable.
Velocity of Propagation (Vp)
Electrical energy travels at the same speed as light in a vacuum. It travels
slower than that everywhere else. The speed that it travels in a cable is often
expressed as the relative velocity of propagation. This value is just a ration
of the speed in the cable to the speed of light (so it is always a number
between 0 and 1). A velocity of propagation value of 0.50 indicates that the
electrical energy moves through the cable at half the speed of light.
Waveform Averaging
(see Noise)